EP Patent Application Publication No. 1 878 379 describes a test tape cassette having a tape guide with a flat support frame on a measuring head that stretches test elements or test fields in a flat manner at the site of measurement. During a measurement, the test tape is bent, starting from deflecting bevels, over the sides of the frame that run perpendicular to the tape direction to achieve a freely stretched flat position. The label-like test elements or test fields used for the measurement have a central chemical carrier the side edges of which are engaged behind by a spreading fabric.
A possible disadvantage is that under the prevailing strains on the test tape structure on the flat support frame, a gap may form between the spreading net and a chemical carrier as illustrated here in FIG. 9. In FIG. 9, gap dimensions are largest in the center and decrease towards the sides, which can generate different capillary forces and ultimately result in undesired distributions (that may have a preferred direction) of the measuring medium.
It has been found that such a gap formation amplifies a tendency for “dewetting” (i.e., a migration of the blood sample from the wetted fabric meshes) and increases a sensitivity towards contaminants present on the skin of the user. The latter effect results from capillary blood collected by a skin puncture that forms a drop of blood at the puncture site in which contaminants are initially concentrated in the boundary area that is in contact with the skin. The “native” blood is then firstly distributed into the boundary areas of the chemical carrier due to the gap formation in the spreading fabric, while the contaminated blood that flows in afterwards then reaches the central measuring spot and can impair the measuring performance.
For the foregoing reasons, there is a need for optimized test tape cassettes, as well as disposable testing means used therein, that provide an improved reliability and accuracy of an analyte measurement.